Nitrogen doped biomass derived carbon dots as a fluorescence dual-mode sensing platform for detection of tetracyclines in biological and food samples.

Nitrogen-doped carbon dots (N-CDs) were synthesized hydrothermally using abundantly accessible pitaya peel and 1,2-ethylenediamine as precursors. N-CDs exhibited favorable photostability, which can serve as a multifunctional nano-sensor for detection of three tetracycline antibiotics (TCs) based on fluorescence (FL) dual-mode sensing strategy. The FL intensity of N-CDs could be rapidly quenched by tetracycline (TC) and oxytetracycline (OTC) based on bandgap transition, inner filter effect (IFE), static quenching (SQ) and electrostatic interaction. While a new finding that FL of N-CDs demonstrated a remarkable enhancement in the presence of chlortetracycline (CTC) with the same detection mechanisms as TC and OTC, also including the aggregation-induced emission (AIE). Furthermore, an easily extensible fluorescence sensor array was developed based on multiple CDs for identifying multiple TCs in real samples. Therefore, the constructed N-CDs provides a new perspective for choosing extensive natural biomass to synthesize CDs, further developing a novel sensor to realize their versatile sensing application.

A facile fluorescence platform for chromium and ascorbic acid detection based on "on-off-on" strategy.

In this paper, a facile and rapid fluorescence "on-off-on" strategy for the detection of chromium (Cr(VI)) and ascorbic acid (AA) was developed, which was based on the water-soluble carbon dots (CDs). The CDs was synthesized by a microwave-assisted treatment of L-tartaric acid, citric acid, and urea. The CDs have many advantages, such as high fluorescence quantum yield (20.5%) and good fluorescence stability. Based on inner filter effect (IFE) and static quenching, the fluorescence of the CDs can be quenched by Cr(VI) quickly; while the reduction of IFE and reducing action can make the fluorescence of the CDs recover by AA efficiently. Moreover, under the optimal experimental conditions, the CDs had a good detection performance for Cr(VI) in the range of 0.8 âˆ¼ 189 µM with the limit of detection (LOD) of 0.16 µM. The linear detection for AA was ranged from 0.43 to 25.7 µM with a LOD of 0.1 µM. More importantly, the as-constructed fluorescence detecting platform was successfully applied for Cr(VI) and AA detection in the environmental samples and fruit samples, respectively. In addition, the application potential of the CDs in fluorescent films and anti-counterfeiting materials was further discussed in detail. This work will provide a novel idea for designing a portable sensor based on the CDs to quickly and sensitively detect Cr(VI) and AA.